This section provides background information related to the present disclosure which is not necessarily prior art.
When the term “flat roof” is used in this specification it is meant to cover roofs that can be horizontal or can be inclined or sloping up to 20°. Often flat roofs are inclined by around 5°.
Packing- and/or transport units are well-known from the prior art. For example DE 10 2008 004 018 A1 discloses a transport unit comprising wedge-shaped roof elements for a sloping roof. In one embodiment the transport unit comprises both ordinary roof elements as well as wedge-shaped elements. DE 10 2008 004 018 A1 describes that the ordinary elements can be arranged above the wedge-shaped elements, so that laying out the roof insulation can be done in an efficient manner.
Furthermore, WO 2012/059192 A1 discloses a packing and/or transport unit comprising several fibrous insulation elements for flat roof insulation being arranged in at least one stack, whereby the stack contains at least two different types of insulation elements, which differ with respect to the material properties. This packing and/or transport unit is easy to handle and allows to arrange most of the materials close to the places where it is to be used. To achieve these advantages the stacked insulation elements comprise lamellae and/or lamella boards having a high compression strength but low point load resistance due to their fiber orientation and at least one insulation board having an even higher compression strength and high point load resistance. This packing and/or transport unit comprises carrying feet made of several insulation board strips arranged on top of each other.
Finally, DE 42 18 354 A1 discloses ways of packaging roof boards in a transport unit using various shapes of carrying feet made of mineral wool. In one embodiment these carrying feet have a trapezoidal cross section. This shape of the carrying feet has the advantage that water for example resulting from rainfall runs of the top surface of the transport unit. Especially in winter it is thereby avoided that freezing water on top of the transport unit damages the foil wrapped around the transport unit. On flat roofs inclined insulations are often installed to direct water from rain and/or snowfall in a certain direction so that the roof can be kept dry most of the time. For this purpose it is well known to use a cut-to-fall roof solution, typically applicable to horizontal concrete decks. Concrete decks are mostly horizontal, so a slope must be provided by the insulation layer. It is well known to arrange one or more layers of plane roof insulation boards and finishing with one or more layers of relatively thin wedge-shaped insulation boards. This solution is time-consuming since many layers must be applied sequentially, and it is therefore also an expensive solution.
Insulation elements are mostly delivered to a roof in a packing and/or transport unit of the type mentioned initially. The number of layers of insulation elements in the packing and/or transport unit depends on the required thickness of insulation which equals the height of the insulation element. It is not desired to have too tall packing and/or transport units, since it is difficult to the workers to pick the insulation elements from such tall packing and/or transport units. Other logistic aspects must also be taken into consideration, in particular the utilization of space on the trucks for transportation. The maximum height of truck spaces is around 2700 mm, and it is desirable to utilize this as much as possible. In practice this means that transport units should be stackable in two layers with a total height of less than around 2700 mm. Thus, each transport unit should be limited to a maximum height to around 1350 mm. Depending on the height of the insulation elements each transport unit can be provided with for example 2, 3, 4 or 5 lamella layers resting on carrying feet.
If there is an even number of layers of insulation elements the transport unit normally has a horizontal upper surface, since it is possible to equal out the sloping surfaces of the stacked insulation elements. However, if the number of layers of insulation elements is uneven the upper surface of the transport unit becomes sloping. Having a sloping top surface of the transport unit is undesirable for various reasons. First of all there is a risk that an upper transport unit will slide on the lower transport unit during transport, when such two transport units are stacked on a truck. Additionally, the upper transport unit should be turned 180° in relation to the lower transport unit in order to equal out the sloping surface of the lower transport unit. This increases the complexity of stacking.